In a typical nuclear medicine diagnostic procedure, a radiopharmaceutical material comprising a radioisotope tracer is administered to a patient. An example of a radioisotope tracer is Technetium-99m, which is a gamma ray emitter. Radiation subsequently emitted by the radiopharmaceutical material inside the body indicates sites at which the tracer has been absorbed.
A detector for measuring the emitted radiation is generally positioned at several locations around the body, and a collimator is placed between the body and the detector so that the approximate direction from which radiation is emitted may be determined. The collimator is made of a material that is opaque to gamma-rays and X-rays, such as lead or tungsten. Channels through the collimator allow radiation emitted from a narrow solid angle to pass through the opaque material.